In this paper a low profile circularly polarized annular ring slot antenna (CPARSA) with high gain is presented. An inverted U-shaped meandered slot is cut at the inner patch of annular ring to obtain the circularly polarized (CP) radiation. This annular slot loaded ground plane on a substrate thickness of 0.5 mm results in a very low profile (0.009λ 0 ) antenna in term of free space wavelength at its center operating frequency. The largest side lengths of octagonal shaped antenna are 0.89λ 0 ×0.89λ 0 according to its center frequency. Measured impedance bandwidth of 23.54% from 5.4 GHz -7.0 GHz (for |S 11 | ≤ −10 dB) and AR bandwidth (AR<3dB) of 5.15% from 5.67 GHz -5.97 GHz are achieved by the antenna. Meanwhile, stable radiation pattern is observed throughout the entire bandwidth with peak gain of 7.6dBi at the center frequency of 5.8 GHz. A defected ground plane is employed in the design which results in reduction of surface waves leading towards higher gain of antenna. The proposed antenna operating at 5.8 GHz band is fabricated on low cost substrate with standard printed circuit board (PCB) process. The proposed design provides favorable characteristics for various lightweight applications including miniaturized drones and airborne applications. To validate the prototype, measured results are compared with simulation outcomes and good agreement is obtained.
A single-fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90 phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz-7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S 11 | < −10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C-band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ 0 × 0.40λ 0 and thickness of 0.02λ 0 where λ 0 is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15-5.85 GHz) and a wide variety of Cband wireless applications.
K E Y W O R D SARBW, circular polarization, microstrip-fed slot, slot antenna, wideband
An intrusion detection system serves as the backbone for providing high-level network security. Different forms of network attacks have been discovered and they continue to become gradually more sophisticated and complicated. With the wide use of internet-based applications, cyber security has become an important research area. Despite the availability of many existing intrusion detection systems, intuitive cybersecurity systems are needed due to alarmingly increasing intrusion attacks. Furthermore, with new intrusion attacks, the efficacy of existing systems depletes unless they evolve. The lack of real datasets adds further difficulties to properly investigating this problem. This study proposes an intrusion detection approach for the modern network environment by considering the data from satellite and terrestrial networks. Incorporating machine learning models, the study proposes an ensemble model RFMLP that integrates random forest (RF) and multilayer perceptron (MLP) for increasing intrusion detection performance. For analyzing the efficiency of the proposed framework, three different datasets are used for experiments and validation, namely KDD-CUP 99, NSL-KDD, and STIN. In addition, performance comparison with state-of-the-art models is performed which suggests that the RFMLP can detect intrusion attacks with high accuracy than the existing approaches.
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